Converting a scanned map into GIS data

John McVay

• My Field of Study: Environmental Science with a concentration in Community Land Planning.

• Career Aspiration: work for a land trust

How can this skill be applied?

• Project that this information comes from prioritized areas for habitat protection – what some land trusts do.

• Sometimes work in remote areas with no previously prepared GIS. Physical map may be all you start with.

• As a planner, you can create new features in GIS by sketching features on the scanned map

But First… You Have to Get Scanned Map Set Up in ArcGIS

How to do this:

• Open scanned image in ArcMap, click yes to build pyramids.

• Set coordinate system

• Determine x,y coordinates for control points

- Zoom in enough so that you can read the coordinates

- Coordinates along the top and y-coordinates down the left side

Adding Coordinates:

• Zoom in • Display the Georeferencing toolbar.• Click the View Link Table button • Click the Add Control Points button • Position the crosshair so that it lines up

precisely with the intersection of the blue tic mark and the black line of the map border.

• Right-click and choose “input X and Y.”

• Enter x and y coordinates

• Once all four coordinates added, to permanently apply the transformation to the data, you must use the “Rectify” command from the Georeferencing menu